Field
The present disclosure relates to systems and methods for suppressing noise generated in an electrocardiographic (ECG) signal displayed on an ECG monitor due to external electrical equipment and, more particularly, to the suppression of noise generated in an ECG signal due to the presence of a powered injector in the vicinity of a patient.
Description of Related Art
Angiography is used generally in the detection and treatment of abnormalities or restrictions in blood vessels. In an angiographic procedure, one obtains a radiographic image of vascular structure with the assistance of a radiographic contrast medium (sometimes referred to simply as contrast) injected through a catheter. The vascular structures in fluid connection with the vein or artery in which the contrast is injected are filled with contrast. X-rays passing through the region of interest are absorbed by the contrast, causing a radiographic outline or image of blood vessels containing the contrast. The resulting images can be displayed on, for example, a monitor and recorded.
With reference to FIG. 1, in a typical medical imaging environment, a patient 100 is positioned in a room that includes an imaging system (not shown) as well as an injection system for injecting contrast and/or saline into the patient. One example of the injection system can include an injector 10 such as the MEDRAD® Stellant® CT Injection System available from the Radiology business of the Pharmaceutical Division of Bayer AG of Indianola, Pa., U.S.A. The injector 10 includes two syringe interfaces 20a and 20b to which two syringes 30a and 30b are removably attachable. Two drive members or pistons 40a and 40b operatively connect to plungers 50a and 50b slidably disposed in syringes 30a and 30b, respectively, to pressurize and inject the fluid therefrom into the patient 100 via a catheter 60 in fluid connection with syringes 30a and 30b. In addition, heater jackets 70a and 70b may be provided to maintain the fluid within the syringes 30a and 30b at a predetermined temperature. As shown in FIG. 1, such heater jackets 70a and 70b may each include an arcuate resistance heater portion configured to snap over the cylindrical body of the syringes 30a and 30b. 
Further details of such injectors, control systems therefor, and injector protocols used therewith are described, for example, in U.S. Pat. Nos. 5,494,036, 6,339,718, 6,643,537, and 6,958,053, the disclosures of which are incorporated herein by reference.
In many instances, a patient scheduled for a scanning procedure may also be connected to a vital signs monitoring system, such as an ECG monitor 80, via a plurality of electrodes 82 attached to the skin of the patient. Each electrode 82 is connected via a lead 84 to the ECG monitor 80. Electrical noise/disturbance(s) are generated as a result of the use of the injector 10 and related equipment. For instance, electrical noise may be generated when the heater jackets 70a and 70b are turned on and off or due to an electrical disturbance (i.e., an ESD field) that may develop during the delivery of a fluid by the injector 10 due to the dissimilarities between the materials used for the barrels of the syringes 30a and 30b (e.g., plastic) and the plungers 50a and 50b (e.g., rubber). This electrical noise can be conveyed from the injector 10 and related equipment to the patient 100 via, for example, a fluid path 55 connecting the injector 10 to the catheter 60, which is conductive by virtue of the contrast medium or saline therein.
Unless this noise is safely routed to earth (low impedance), the noise will be picked up by the electrodes 82 of the ECG monitor 80. The noise/electrical disturbance then causes a distortion 86 of the ECG signals displayed on the ECG monitor 80. This is because the noise that is generated by the injector 10 and related equipment occupies the same part of the electromagnetic/frequency spectrum as the electrical (cardiac) signals generated by the heart of the patient 100.
Accordingly, a need exists for a system to safely route to ground noise generated by external electrical equipment, such as a powered injector system, positioned in proximity to a patient connected to an ECG monitor such that this noise is prevented from causing distortions in the ECG signals that are displayed on an ECG monitor.